1. Field of the Invention
This invention relates generally to the mounting of parts, for example, of a tape recorder or other apparatus, on a metal chassis or base plate by means of synthetic resin mounting members molded through holes in the base plate so as to be permanently joined in the latter.
2. Description of the Prior Art
It has been the usual practice to provide small tape recorders or other apparatus with a chassis which is molded of synthetic resin and which has metal pins, shaft bushings and the like inserted and anchored in the chassis during the molding of the latter. In order to provide a molded synthetic resin chassis with the requisite strength and rigidity, the molded chassis must be of substantial thickness, and such requirement interferes with the miniaturizing of the associated apparatus. Further, with the described arrangement employing a synthetic resin chassis with metal pins, shaft bushings and other inserts inserted in the chassis during the molding thereof, considerable difficulty and hence relatively high costs, are involved in positioning the metal inserts for the molding operation and in mounting and securing various separately formed various parts in respect to such metal inserts.
In view of the above problems associated with a chassis molded of synthetic resin and having metal inserts anchored therein, there has been recently adopted a so-called "outsert" system in which the chassis or base of the apparatus is formed of a metal plate and mounting members of synthetic resin are molded through holes in the metal plate so as to define pins, shafts and supporting lugs or posts at one side of the metal plate, for example, as disclosed in U.S. Pat. No. 3,248,867, and in the article entitled "One-shot Plastic-to-Steel Molding Improves Clock Design" beginning at page 91 of MACHINERY, February, 1965. In order to permanently and securely join each of the synthetic resin mounting members to the metal base plate or chassis, each mounting member includes a support portion in the form of the desired pin, shaft, lug or post molded against one surface of the base plate at an area of the latter extending outwardly from the respective hole, a root portion molded against the opposite surface of the base plate at an area of the latter also extending outwardly from the respective hole, and a connecting portion molded in the hole simultaneously with the support and root portions so as to be integral therewith. By reason of the inherent strength of the metal forming the base plate or chassis, the thickness of the latter can be minimized so as to adapt the resulting combination of the chassis or base plate and mounting members for inclusion in a miniaturized apparatus. Since the several mounting members of synthetic resin can be molded simultaneously in respect to the metal base plate or chassis, the combination of the base plate or chassis and the several mounting members can be economically and easily produced.
However, the existing "outsert" system for providing molded mounting members integrated with a metal base plate or chassis has a number of limitations that restrict the use thereof and prevent realization of the maximum economies possible in assembling various parts on the chassis by means of the mounting members. More particularly, when molding the mounting members, the metal chassis or base plate having holes therein is disposed between a pair of dies and melted resin is forced to flow into cavities opening at the faces of the dies at the locations of the holes so as to form the support portions in the form of pins, shafts, lugs or posts in the cavities of one die, while the root portions of the mounting members are formed in the cavities of the other die and connected to the respective support portions through the holes in the metal base plate or chassis. If one or both of the dies is provided with a recess in the face thereof for receiving the metal base plate or chassis with the intention that, during molding, the peripheral portions of the dies will abut each other about the perimeter of the base plate or chassis, variations in the thickness of the metal base plate or chassis which are within accepted manufacturing tolerances may nevertheless result in a gap between the peripheral portions of the dies which are intended to abut or in gaps between the faces of the dies and the confronting surfaces of the metal base plate or chassis so that undesirable flashes of the resin will be formed in such gaps. In order to avoid the formation of the flashes, it is necessary that at least the peripheral portions of the dies abut against the opposite surfaces of the metal base plate or chassis during the molding of the mounting members. By reason of the foregoing, the mounting members, as molded in cavities of the dies, cannot extend beyond the perimeter of the base plate or chassis. Thus, the overall size of the base plate or chassis and the size of the dies required for the molding of mounting members through such base plate are dictated by the sizes and spacing of the parts to be supported or mounted by the mounting members on the base plate or chassis.
Furthermore, with the existing "outsert" system, additional locking or fastening elements are required for securing parts on the molded mounting members. For example, if a slide member is to be mounted for longitudinal movement in respect to the metal base plate or chassis, the respective molded mounting members provided for that purpose usually have their support portions in the form of posts terminating in reduced diameter guide pins which are slidably received in longitudinal slots of the slide member. When assembling the slide member on the molded posts extending from the chassis, it is customary to install E-rings on the reduced diameter ends or guide pins of the posts after the latter have been extended through the slots of the slide member so as to prevent removal of the slide member from such guide pins. The use of such E-rings or other fastenings for securing the slide member or other part on the mounting members increases the number of elements and time required for the assembly.